Elimination of loess collapsibility by the compaction effect of pipe pile

• Pipe pile driving significantly densifies collapsible loess and eliminates collapsibility within a range of three pile diameters. • The compaction effect induces irreversible plastic deformation in loess, consistent with cavity expansion theory predictions. • Void ratio decreases and dry density increases nonlinearly with decreasing distance from the pile center. • In-situ SPT and CPT results confirm substantial improvements in soil and single-pile bearing capacity after pile installation. • A funnel-shaped pipe pile is proposed, increasing single-pile side resistance by more than four times while eliminating loess collapsibility. The collapsible Loess foundation at the easternmost end of the Loess Plateau was selected as the research object to explore the elimination effect of Loess collapsibility during the process of pipe pile driving. The results show that the compaction effect plays a role in changing the physical and mechanical parameters of Loess. With the increase in distance from the center point of the pile, the void ratio and dry density of the soil between the piles show a nonlinear increase and decrease trend, respectively, and change significantly within the range of three times the diameter. For medium collapsible loess, the collapsibility of loess with a considerable burial depth has been completely eliminated, the collapsibility of loess with shallow burial depth has been completely eliminated or reduced from moderate to slight. Based on cavity expansion theory, the distance between piles required to eliminate the collapsibility of Loess should not exceed three times the diameter, beyond which soil plastic deformation may occur. Further combining the results of in-situ standard penetration and cone penetration tests, it is concluded that the bearing capacity of the soil between the piles and the single pile has been significantly improved. These findings provide theoretical and data support for the foundation treatment of medium collapsible Loess in the easternmost region of the Loess Plateau in China.